Method of manufacturing composite sheets



' Nov. 3, 1931.

H. W. COOPER METHOD OF MANUFACTURING COMPOSITE SHEETS Filed Nov. s, 1927 2 Sheets-Sheet l Nov. 3, 1931.

2 Sheets-Shee't 2 MSWI Filed Nov. 3, 1927 Patented Nov. 3, 1931 maren STATES PATENT ori-ICE HENRY "W". CPER, OF lll/'EST VlE'ilWh, MASSACHSTTS, ASSIGNOR TO NEW ENGLAND v MICAVCO., F TALTHAM, MASSACHUSETTS, A GQBPORAT'JOH GF MASSACHUSETTS METHOD 0F MANUFACTURNG COMPOSITE SHEETS Application led November' 3, 1927. Serial No. 230,892.

lhe present invention relates to the manufacture ci composite sheetsof Hake material and especially to the production ot manufactured mica plate consisting of stratified mica films used in insulating electrical apparatus.

In one of its aspects, the invention consiste in a novel method in accordance with which the constituent flakes of the'required meet are completely assembled in a dry condition, then immersed in a bath of liquid ad- .hesive and finally solidified by pressure to form a sheet. rl`his method has been developed with, satisfactory results to a point 1ere it produces stratilied micaplate more lily, at less erpense and witha smaller iption et adhesive than has been posv the methods heretofore known.

ing the method of my invention, been found desirable to retain the assembly ci dry iiakes against displacement V.. ci

while it is being permeated or otherwise treated with the adhesive; Preferably, therefore, l include in the method the step et engaging and retainingthe assembled flakes against displacement on their supporting surface while they are carried through a bath of liquid adhesive;

Another important step, which I alsol pre- *l'er to include lin practicing my novel method, consists in solidifying the cohercd flakes into sheet form by pressure applied while the assembly remains engaged and retained against displacement.

The disclosure herein includes an improvedV machine by which the method above described may be practiced in an advantageous manner. As herein shown, the machine comprises a conveyor upon which flakes of mica or the like may be assembled, a traveling apron for progressively engaging the assembled Llakes and retaining them against displacement on the conveyor, and a. bath of liquid adhesive disposedv in the path of' the conveyor and apron and in which the'assembled flakes maybe immersed while Vheld in position between the conveyor and apron. As above stated, 1t has been found desirable to; solidify the cohered assemblyV of flakes while retained against displacement uponl` the conveyor whereon they have been assembled. To this end, another feature of the machine consists in pressure rolls so designed andlocated as to engage the conveyor and apron as they emerge from the adhesive bath carrying the cohered iiakes and to press'the two together to solidify the sheet material Vbetween them.

.".lhe novel method and the construction oit' the machine by which the method may be practised will be best understood and appreciated from the following description of preferred embodiment of the machine, selected for purposes of illnstration and shown inthe accompanying drawings, in which Fig; l is a view in side elevation ci the portion of the machine for applying adhesive to the akes carried by the conveyor and compressing them intoa sheet;

Fig". 2 is a sectional View of the same portion. of the machine;

Fig. 3 is a plan view of the same the machine; and Y Fig. 4 is a view in side elevation, on a reduced scale, showing more or less diagrammatically the entire machine up to the inspection table. I

. The machine comprises an elongated frame upon which the diderent mechanisms of the machine are assembled. These'comprise an endless conveyor extending the full length of the frame, bins and sifting mechanism located at one end of the frame for supplying portion of Vmica flakes to the conveyor, a tank and associatedmechanism for applying liquid adhesive to the flakes showered on the conveyor, and means for compressing and compacting the cohered flakes into an integral sheet.

These elements of the machine will be described in the order in which they have been enumerated. The main frame of the machine is built up of pairs of angle iron posts or legs 22, ,connected by cross bars, not shown, and by long horizontal side bars 2l. The conveyor is made up of a pair of spaced sprocket chains 24E to which are connected the edges of a web of Vi'oraminons material, preferably a wire mesh cloth 25 having about four meshes to theinch. The chains of the conveyor are supported and driven by a series of all` of the sprocket wheels 26 in a counter clockwise direction, so as to advance the upper pass of the conveyor from right to left, as seen in the drawings. The lower pass of the conveyor is supported by idle rolls 251 journaled between each pair of legs 22.

at the right-hand end of the frame and above the conveyor is located a number of bins 4:0, two of which only are shown in Fig. Each of the bins contains two oscillating cradles l2 with perforated walls of expanded metal, having openings `of appropriate dimensions and adapted in their oscillation to sift out and shower mica flakes upon the conveyor passing beneath them. rlhe flakes are supplied in bulk to these cradles through suitable ducts #la extending into the bins el() from a source of supply, not shown. Each of the cradles is carried by a transverse shaft 48, having a toothed segment 46 at one end, meshing with a horizontally disposed reciprocating rack l48 guided by spaced pairs of rollers i9 and actuated from a crank disc 5l through a connecting rod 53. The crank disc is carried by a transverse shaft 55, driven by a belt 57 from a motor 59 orrot-her convenient source of power. Clutch mechanism, controlled by a handle el?, is provided for throwing each cradle into or out of operation in accordance with the requirements of the work in hand. A

The mechanism above described is indicated in Fig. 4 diagrammatically rather than structurally but will be apparent that the conveyor, in traveling toward the left beneath the bins 40, accumulates a. layer of mica flakes which is increased in thickness it pro jresses into the range of each of the cradles 42. On account of the foraminous nature of the conveyor, dust and flakes of insufiicient size for the required purpose are sifted out of the lower layer of the flakes, so that only flakes larger than the mesh of the conveyor are carrie-il away from the first bin. rlhe action of the cradles and their rate of supply is so controlled that the layer of flakes, as it passes from the left-hand loin of the series, is built up to the required thickness and constitutes a loose, dry assembly of material before the operation of binding the flakes together takes place.

l, 2 and -l illustrate in somewhat greater structural detail that portion of the machine wherein adhesiveis supplied to the layer of flakes assembledL on the conveyor in the manner above set forth. The main frame of the machine carries an elongated tank 50, located to the left of the last bin Ll-.O of the series and in such position that the conveyor can be deflected into the adhesive 52 which the tank contains, which may be shellac or any other suitable liquid binder. To this end, guide rollers 54 are provided which lead the conveyor to the wall of the tank 50, then deflect it downwardly below the surface of the shellac and finally guide it back into its original path as it leaves the tank. The rollers 54C are journaled 'in the side bars 2l and provided with sprocket wheels at each end which mesh with the chains of the conveyor so that the rollers are driven at the sani-e surface speed as the conveyor.

ln order to prevent displacement or floating away of the mica flakes as these are carried into the shellac by the conveyor, provision is made for engaging the flakes at the exposed .face of the layer and holding them in place upon the foraminous web 25. rlhis is effected by an endless apron of wire mesh cloth 60, which is guided into engagement with the upper surface of the layer of mica flakes on the conveyor web as the latter enters the tank 50. For this purpose, a series of three drums 62, 63 and Gil is provided for driving and guiding the apron G0 in the dcsired path. The drum 6:2 is carried by a transverse shaft 65, journaled in suit-able shaft hangers 66, bolted to the side rails 2l of the frame and carrying sprocket wheels GS at. its outer ends which mesh with and are driven by the sprocket chains of the conveyor.

he dr in 6l is similarly mounted upon a shaftt?, journaled in hangers 69, and is similarly driven hy the conveyor chains through the sprocket wheels 7l. The drum G4 serves to guide the apron GO into contact with the material on the conveyor web 25, automatically and progressively covering said material. i

The center roll 63 is an idle roll and is constructed and arranged to maintain suitable yielding tension upon the apron 60. To this end, it is jeurnaled in sliding boxes T0, mounted for vertical movement in slotted hangers 72, secured to the rail 2l, and having .its weight compensated to some extent by compression springs Til disposed beneath the boxes.

The apron 60 is maintained in contact with the conveyor web 25 throughout the course of its travel in the shellac bath and until after it has emerged therefrom. The roller 54:, located at the left end of the tank 5th cooperates with presser roller 8O for i'nessing, compacting and solidifying the adhesive pci'- meated layer of mica flakes as it is carried out of the shellac bath between the conveyor web 25 and the apron 60 and also for stripping surplus shellac from the sheet, so that it may be returned to the tank. ri`hc roller is carried by a shaft 82, journaled in boxes .nou

84, mounted in a pair of slotted hangers 86, secured to the side rails 21 of the frame. Each box is urged upwardly bya compression spring located beneath it but may be moved downwardly to exert a predetermined but controllable amount of pressure upon the layer of mica by a hand screw 88 provided for that purpose.

As the solidified mica sheet 90 is carried beyond the drum 62, the apron 60 is stripped from it and the sheet is carried forward, eX- posed upon the conveyor Where it may be conveniently inspected and eventually cut into smaller sheets of commercial sizes.

In my co-pending application Serial No. 230,891 filed of even date herewith I have shown a complete mica plate laying machine, including a light table for inspection and rectiflcation of the sheet, of the same general design as is partially illustrated by Fig. l of this application but differing therefrom in that means is provided for applying adhesive binder to each layer of the mica flakes as they are successively showered upon the conveyor. The herein illustrated machine, for practising the method of supplying binder at one operation to a dry assembly of the mica flakes as claimed herein, may be substituted in the machine of my co-pending application for the mechanisms employed for effecting said step-by-step application of the binder With a saving of the binder and an increased dielectric strength in the finished plate. Accordingly generic claims to the complete machine and method of manufacture Will be found in my co-pending application Serial No. 230,- 891, the claims of this application being confined to the alternative method of supplying the binder.

The steps of the method of my invention as carried out in connection With the machine disclosed Will be apparent from the foregoing description but may be briefly stated as follows. The constituent mica flakes are assembled to the desired thickness upon the surface of the conveyor as it passes beneath the bins 40. This dry material is then automatically and progressively engaged and retained against displacement vby the apronGO. While so retained, it is carried through the adhesive bath in the tank 50 and before being released or uncovered is compressed into an integral or coherent sheet by the pressure rolls 54 and 80. The sheet 9() thus formed is then uncovered by the apron 60 and is ready for further treatment in its manufactured form.

It vvill be apparent that the machine herein disclosed may be used to good advantage for carrying out the method of my invention, but such method is not in any sense dependent upon this or any particular machine construction but may be practiced in connection With any apparatus suitable for its various steps.

i In a divisional application Serial'No. 386,052

ment, `permeating the Yflakes `with adhesive While so retained, andpvithout releasing the cohered flakes, solidifying them by pressure to form an integral sheet.

2. The method of making composite sheets which consists in assembling the constituent flakes upon a movable surface, holding the material thus collected against displacement upon said surface, immersing the assembled flakes in a bath of liquid adhesive While so held, and then sohdifying the cohered mass to form an integral sheet. ,Y

3. The method'of making composite sheets Which consists in showering the constituent flakes upon a supporting surface forming a complete, dry, loose assembly for the required sheet, immersing the material thus collected With its supportingk surface in a bath of liquid adhesive, and then removing surplus adhesive and solidifying the sheet by pressure.

A 4. The method of making composite sheets which consists in showering the constituent flakes upon a movable surface, forming progressively a complete, dry, loose assembly for the required sheet, progressively immersing the material thus collected with its supporting surface in a bath of liquid adhesive, and then removing surplus adhesive and solidifying the sheet by pressure.

5. The method of making composite sheets upon a traveling conveyor which consists in assembling the constituent flakes upon said conveyor, retaining said flakes against relative displacement by pressure, leading them,V

While so retained, through a bath of Vliquid adhesive and, Without releasing such retaining pressure, subjecting the adhesive permeated mass to a furthersohdifymg pressure.

6. The method of manufacturing an end- V less sheet of stratified mica films Which comprises continuously producing a layer of mica films of substantially uniform thickness, progressively engaging said layer between foraminous coverings and passing the covered layer through a bath of liquid binder, and then solidifying the layer by pressure.

7 The method of manufacturing a plate of stratified micay films Which comprises building up a layer of dry mica films` to the desired thickness, and immersing said layer of mica', films in a bath of liquid binder While holding the layerbetvveen coverings of foramifiled (August 15, 1,929- I `have claimedM the ma-n` nous material to retain the films against relative displacement While permitting the binder to permeate through the layer.

8. The method of manufacturing a plate of stratified mica films which comprises building up a layer of dry mica films to the desired thickness, immersing said layer of mica lms in a bath of liquid binder While holding the layer between coverings of foraminous material to retain the films against relative displacement While permitting the binder to permeate through the layer, and then subj eeting the layer to pressure While still between said coverings.

HENRY W. COOPER. 

